The primary goal of the proposed research program is to establish the functional contribution of integrins and ECM molecules to the morphogenetic processes that help shape the early the early amphibian embryo. In order to better understand integrin function and expression in embryogenesis, Xenopus integrin alpha subunit specific cDNAs and antibodies will be obtained. Immunocytochemistry and in situ hybridization methods will be utilized in order to determine the spatial and temporal patterns of integrin mRNA and protein expression in embryos. Several approaches will then be employed to analyze the functions of specific integrin receptors. Integrin transcripts will be injected into eggs and specific blastomeres and the adhesion, migration and fate of the progeny determined as development proceeds. The adhesive and migratory behaviors of embryonic cells over-expressing control and dominant- negative integrin constructs will be compared. Changes in integrin mediated cell adhesion in response to induction will be studied using cells and explants derived from embryos injected with transcripts encoding peptides known to induce mesoderm. The control of integrin expression and/or the activation of integrin ligand binding activity in activin-induced tissues will also be investigated at the mRNA and protein levels.